1. Field of the Disclosure
The present invention relates to liquid crystal display devices, and, more particularly, to a liquid crystal display device and a method for fabricating the same, which has a structure applied thereto for preventing a liquid applied to a substrate from passing through a display portion to encroach even to a seal pattern portion causing seal breakage or gap defect.
2. Discussion of the Related Art
In a current information oriented society, as a visual information transmission media, importance of the display devices are being emphasized further, and, in order to take a major position hereafter, the display devices are required to fulfill necessary conditions of low power consumption, thin, high definition, and so on.
In the display devices, there are light emission types that emit lights for themselves, such as a cathode ray tube CRT, an electro luminescence EL, a light emitting diode LED, a vacuum fluorescent display VFD, a field emission display FED, a plasma display panel PDP, and so on, and non-light emission types that can not emit the light for themselves, such as a liquid crystal display device LCD.
Of the display devices, since the liquid crystal display device, a device for displaying an image by using an optical anisotropy of liquid crystals, has a visibility better than the cathode ray tube, an average power consumption lower than the cathode ray tube of the same screen size, and lower heat generation, the liquid crystal display device is spot lighted as a next generation display device together with the plasma display panel and the field emission display FED.
In general, the liquid crystal display device is a display device in which picture signals are supplied to a matrix of pixels respectively, for displaying a desired picture by controlling light transmissivities of the pixels. For this, the liquid crystal display device is provided with a lower substrate having thin film transistors arranged thereon and an upper substrate having color filters formed thereon bonded together with a liquid crystal layer disposed therebetween. The lower substrate and the upper substrate have polarizing plates formed on surfaces thereof for blocking the light or controlling transmission of the light depending on a direction of incidence of the light.
The lower substrate and the upper substrate have alignment films formed at uppermost layers respectively for fixing an initial orientation of the liquid crystals.
A process for bonding the upper substrate and the lower substrate to fabricate one liquid crystal display panel thus is called as a cell process. The cell process has an alignment step for forming the alignment films to orient the liquid crystals on the lower substrate having thin film transistors arranged thereon and the upper substrate having color filters formed thereon in the same direction, a bonding step for bonding the two substrate with a fixed cell gap therebetween maintained, a sealing step for injecting the liquid crystals between the upper and lower substrates, and a cell cutting step for separating into the liquid crystal panels.
Thereafter, upper/lower polarization plates are attached to front/rear surfaces of the liquid crystal display panel respectively. The polarization plate is formed in a state a protective film is attached thereto, and the polarization plates are attached thus after the protective film is removed from each of the polarization plates with an absorber and peeling unit.
A related art liquid crystal display device will be described with reference to the attached drawings.
FIGS. 1A and 1B illustrate a section and a plan views of a related art liquid crystal display device after coating an alignment film, respectively.
Referring to FIGS. 1A and 1B, in formation of the alignment film on a substrate in the related art liquid crystal display device, after coating alignment film liquid 15, the alignment film liquid is dried in a baking step to form the alignment film. At first, at the time the alignment film liquid 15 is being coated, the alignment film liquid 15 passes a portion to coat the alignment film thereon actually due to spreadability of the alignment film liquid 15, and, if the spreadability is excessive, the alignment film liquid 15 fails to return to the portion to coat the alignment film thereon, but remains to encroach even a portion where a seal pattern is to be formed, later.
If the alignment film liquid 15 encroaches the portion where a seal pattern is to be formed, the alignment film liquid 15 is hardened in the baking step remaining as the alignment film on the portion where a seal pattern is to be formed, to cause a gap defect as much as a height of the alignment film at a portion the alignment film and the seal pattern overlap, and a tendency of peeling of the seal pattern from the alignment film due to poor adhesiveness of the seal pattern to the alignment film, or seal breakage. It is understood that a cause of the defect is meeting of the seal pattern and the alignment film due to failure of return of the alignment film liquid 15 into the portion to coat the alignment film thereon after the encroach.
Thus, the related art liquid crystal display device has the following problems.
In a case of an alignment film formed on the substrate in a liquid state by liquid handling step, if the alignment film liquid passes a predetermined coating portion, the alignment film liquid can encroach into a portion to form a seal pattern thereon, and, once the alignment film liquid encroaches the portion to form a seal pattern thereon, return of the alignment film into the predetermined coating portion is difficult, remaining in the portion to form a seal pattern thereon. In this case, if the alignment film baked thus and the seal pattern meet, a defect of light leakage takes place at this portion due to peeling of the seal pattern, seal breakage, or gap defect. Consequently, an effort for preventing this from taking place is required.